Move to London, then rent a mobility scooter with a large trailer. Go to a rich borough and start collecting computers :)Otherwise, look on gumtree for some computers or other free stuff in the freebies section.

I would just ask around, for instance my Grandpa was getting rid of an old computer and he was happy to just give it to me. Let your family/friends know that you would take one, and I bet they would let you know if they are getting rid of one or know someone who is. Good luck in your search:)